Re: how can I do this in gmake?

[Maxim Yegorushkin]

ma wrote:
> "Maxim Yegorushkin" <address@hidden> wrote in message 
> news:address@hidden
> > ma wrote:
> >
> > > I am writing a make file that will be used on several development. in 
> > > each
> > > development, there are a huge amount of file that needed to be built but
> > > only a small part of them is changing and others are  not changing. I put
> > > all of these files into a library. The idea is that when the user run 
> > > make
> > > file for the first time, it will create all of the source files and then
> > > create library and copy somewhere in the system. On any other call to 
> > > this
> > > make file (maybe from some other directory that doesn't have  *.obj files
> > > related to library in it), it checks if the lib exist, use it and if not
> > > create it.
> > This may help you:
> >
> > address@hidden tmp]$ cat Makefile
> > all :
> >
> > libmy_obj := a.o b.o
> > lib/libmy.a : $(libmy_obj) | lib
> >
> > foo_obj := foo.o
> > bin/foo : $(foo_obj) lib/libmy.a | bin
> > bin/foo : LDFLAGS += -Llib -lmy
> >
> > bar_obj := bar.o
> > bin/bar : $(bar_obj) lib/libmy.a | bin
> > bin/bar : LDFLAGS += -Llib -lmy
> >
> > bin/% :
> > $(CC) -o $@ $($(@F)_obj) $(LDFLAGS)
> >
> > lib/% :
> > ar r $@ $($(@F)_obj)
> >
> > .PHONY : all clean
> >
> > all : lib/libmy.a bin/foo bin/bar
> >
> > lib bin :
> > mkdir -p $@
> >
> > clean :
> > rm -rf *.{c,o} lib bin
> >
> > # create dummy source files
> > a.c b.c :
> > touch $@
> > %.c :
> > echo "int main() {}" > $@
> >
> > address@hidden tmp]$ make
> > touch a.c
> > cc    -c -o a.o a.c
> > touch b.c
> > cc    -c -o b.o b.c
> > mkdir -p lib
> > ar r lib/libmy.a
> > ar: creating lib/libmy.a
> > echo "int main() {}" > foo.c
> > cc    -c -o foo.o foo.c
> > mkdir -p bin
> > cc -o bin/foo foo.o -Llib -lmy
> > echo "int main() {}" > bar.c
> > cc    -c -o bar.o bar.c
> > cc -o bin/bar bar.o -Llib -lmy
> > rm bar.c foo.c
> > address@hidden tmp]$ make bin/foo
> > make: `bin/foo' is up to date.
> > address@hidden tmp]$ rm lib/libmy.a
> > address@hidden tmp]$ make bin/foo
> > ar r lib/libmy.a
> > ar: creating lib/libmy.a
> > cc -o bin/foo foo.o -Llib -lmy
>
> Thanks.
> I belive the main trick that used here is
>
> lib/libmy.a : $(libmy_obj) | lib
>
> which I think telling that if lib is uptodate, don't go for $(libmy_obj) 
> prerequiatic else go and use that pre requistic. Am I wring?

bin/foo : $(foo_obj) lib/libmy.a | bin
bin/bar : $(bar_obj) lib/libmy.a | bin

The above two targets depend on lib/libmy.a. Whenever they are built 
lib/libmy.a will also be built if it's not up to date.

I'm bad explaining things in comparisons with the make's clear 
documentation. http://www.gnu.org/software/make/manual/make.html.gz#Rules